This invention relates to communication disruptants which interfere with the copulation of insect pests and thereby control the infestation of larvae, and more particularly to communication disruptants which are effective against insect pests of the family Tortricidae.
Generally, all components of a natural sex pheromone are frequently used in communication disruptants. However, in the case, for example, of communication disruptants for species belonging to the family Tortricidae and having (Z)-11-tetradecen-1-yl acetate as a component of their sex pheromone composition, (Z)-11-tetradecen-1-yl acetate alone has been used without regard to the other components of the sex pheromone of the species. The addition of other components has been said to bring about no improvement in effectiveness.
However, when a communication disruptant containing (Z)-11-tetradecen-1-yl acetate as the only active ingredient is continually used for a period of 5 to 10 years, a phenomenon has been observed in which its communication-disrupting effect on insect pests, particularly of the family Tortricidae, living in the field or the like through successive generations is reduced. Accordingly, it is eagerly desired to develop a new communication disruptant which is also effective for such fields where the communication-disrupting effect (on insect pests, particularly of the family Tortricidae, living there through successive generations) has been reduced.
As a result of extensive investigations on communication disruptants comprising (Z)-11-tetradecen-1-yl acetate and other sex pheromone components, the present inventors have now completed the present invention.
Thus, the present invention provides, for use in the control of insect pests having (Z)-11-tetradecen-1-yl acetate contained in their sex pheromone, a communication disruptant containing (Z)-11-tetradecen-1-yl acetate and the maximum component in the composition of the sex pheromone excepting (Z)-11-tetradecen-1-yl acetate, wherein the weight percentage of the maximum component in the communication disruptant is equal to a value obtained by multiplying the weight percentage of the maximum component in the sex pheromone by a number in the range of 0.02 to 0.5.
The communication disruptant of the present invention makes it possible to control target insect pests while omitting or decreasing the use of an insecticide therefor. Consequently, it has the great merit of being economically advantageous, yielding pesticide-restricted crops, and hence contributing to the securement of safety for human beings.
The communication disruptant of the present invention contains both (Z)-11-tetradecen-1-yl acetate and the maximum component in the composition of the natural sex pheromone excepting (Z)-11-tetradecen-1-yl acetate. Preferably, the weight percentage of the maximum component in the communication disruptant is equal to a value obtained by multiplying the weight percentage of the maximum component in the natural sex pheromone by a number in the range of 0.02 to 0.5 and more preferably 0.02 to 0.3. If the number is less than 0.02, the resulting communication-disrupting effect will be insufficient, while if the number is greater than 0.5, the resulting communication-disrupting effect will be reduced contrariwise.
The maximum component excepting (Z)-11-tetradecen-1-yl acetate is defined as follows: Where the natural pheromone contains a plurality of components in addition to (Z)-11-tetradecen-1-yl acetate, the component having the highest weight percentage of all components but (Z)-11-tetradecen-1-yl acetate is the maximum component. Where the natural pheromone contains only one component in addition to (Z)-11-tetradecen-1-yl acetate, that component is the maximum component.
In the communication disruptant of the present invention, the maximum component preferably comprises (Z)-9-tetradecen-1-yl acetate, (Z)-9-dodecen-1-yl acetate or (E)-11-tetradecen-1-yl acetate.
The communication disruptant of the present invention is effective in disrupting the communication of insect pests of the family Tortricidae and, in particular, the subfamily Tortricinae. Specific and preferable examples of such insect pests include Adoxophyes orana (summer fruit tortrix), Adoxophyes sp. (smaller tea tortrix), Pandemis limitata, Pandemis pyrusana, Pandemis heparana, Archips breviplicana (Asiatic leafroller), Archips fusscocupreana (apple tortrix), Archips podana, Argyrotaenia velutinana, Choristoneura rosaceana, and Homona magnamina (oriental tea tortrix). More specifically, the communication disruptant of the present invention is particularly effective in disrupting the communication of insect pests of the family Tortricidae to fruit trees or tea trees, including the summer fruit tortrix which is an insect pest detrimental to apple, pear, peach, ume (Japanese apricot) and cherry trees, the Asiatic leafroller which is an insect pest detrimental to apple, pear and like trees, and the oriental tea tortrix and smaller tea tortrix which are insect pest detrimental to tea leaves.
The natural sex pheromone components and distribution of principal insect pests of the family Tortricidae are shown in Table 1, and the chemical formulae of those components are given below.
The synthesis of various geometrical isomers used in the present invention, such as (Z)-11-tetradecen-1-yl acetate, (Z)-9-tetradecen-1-yl acetate, (Z)-9-dodecen-1-yl acetate, (E)-11-tetradecen-1-yl acetate and 10-methyldodecyl acetate, can be carried out according to conventionally known processes.
Moreover, in order to prevent oxidation or decomposition of the communication disruptant of the present invention, antioxidants or ultraviolet absorbers may be used therein as required.
Useful antioxidants include, for example, di-tert-butylhydroxytoluene (BHT), vitamin E and 2,5-di-tert-butylhydroquinone (DBH).
Useful ultraviolet absorbers include, for example, 2-(2xe2x80x2-hydroxy-3-tert-butyl-5-methylphenyl)-5-chlorobenzotriazole and 2-hydroxy-4-octoxybenzophenone (HOBP).
Antioxidants and ultraviolet absorbers may each be used in an amount of 0.1 to 5.0% by weight, preferably 1.0 to 3.0% by weight, based on the communication disruptant. If the amount is less than 0.1% by weight, the resulting communication disruptant will have poor stability and hence a short useful life. Even if the amount exceeds 5.0% by weight, no substantial difference in stability will be made.
In preparing the communication disruptant of the present invention, well-known polyethylene tubes are filled with a synthetic pheromone in an amount of 80 to 240 mg per tube according to a technique associated with small tubes for the controlled release of a pheromone (Japanese Patent Provisional Publication No. 57-9705/xe2x80x282) and a technique for giving shape thereto (Japanese Patent Provisional Publication No. 57-156403/xe2x80x282). The duration of its communication-disrupting effect generally ranges from 3 to 6 months, depending on such conditions as the configuration of the field to which it is applied.
The communication disruptant of the present invention is preferably applied in an amount of 50 to 500 tubes per 10 ares. This range may vary according to the area of application, weather conditions, conditions of location (e.g., the configuration of the field), and the form of the communication disruptant. For example, in the case of a field whose area is as large as 1 ha or more and where the velocity of wind is low, the number of tubes used may be slightly decreased.
The communication disruptant of the Resent invention is sealed in polyethylene tubes, so that it permeates through the wall of the tube, evaporates from the outer wall surface of the tube, and is thereby released slowly and persistently into the atmosphere (air) of the field.